For the arrival sensor battery, I recommend looking up the AA battery pack hack for extended life.
I have tried several safeguards against false-triggers. First is to check if the sensor has been away for 15 minutes (may need to tweak based on driving habits and likely power outages). Second, my wife and I use Life360 to minimize the number of "where u" texts. Not recommending Life360 specifically (many express privacy concerns), but it is one tool that provides additional validation that one of us left with a vehicle.
